In IEEE, Wi-Fi™ (also known as wireless local area network (WLAN); these terms will be used interchangeably throughout this document) is standardized in the IEEE 802.11 specifications (IEEE Standard for Information technology—Telecommunications and information exchange between systems. Local and metropolitan area networks—Specific requirements. Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications). Wi-Fi™ is a technology that currently mainly operates on the 2.4 GHz or the 5 GHz band.
The IEEE 802.11 specifications regulate the STA (station, access points or wireless terminals) physical layer, MAC layer and other aspects to secure compatibility and inter-operability between access points and WCDs, (hereinafter referred to as user equipments (UEs)). Wi-Fi™ is generally operated in unlicensed bands, and as such, communication over Wi-Fi™ may be subject to interference sources from any number of both known and unknown devices. Wi-Fi™ is commonly used as wireless extensions to fixed broadband access, e.g., in domestic environments and hotspots, like airports, train stations and restaurants.
Recently, Wi-Fi™ has been subject to increased interest from cellular network operators, not only as an extension to fixed broadband access. The interest is mainly about using the Wi-Fi™ technology as an extension or alternative to cellular radio access network technologies to handle the always increasing wireless bandwidth demands. Cellular operators that are currently serving mobile users with, e.g., any of the 3rd Generation Partnership (3GPP) technologies (e.g., Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS)/Wideband Code Division Multiple Access (WCDMA), High Speed Packet Access (HSPA) or Global System for Mobile Communications (GSM)) see Wi-Fi™ as a wireless technology that can provide good support in their regular cellular networks. The term “operator-controlled Wi-Fi” points to a Wi-Fi™ deployment that on some level is integrated with a cellular network operator of an existing network. In some cases, the 3GPP radio access networks and the Wi-Fi™ wireless access network may even be connected to the same core network and provide the same services.
There is currently quite intense activity in the area of operator-controlled Wi-Fi in several standardization organizations. In 3GPP, activities to connect Wi-Fi™ access points to the 3GPP-specified core network is pursued, and in the Wi-Fi alliance (WFA) activities related to certification of Wi-Fi™ products are undertaken, which to some extent also is driven from the need to make Wi-Fi™ a viable wireless technology for cellular operators to support high bandwidth offerings in their networks. The term Wi-Fi™ offload is commonly used to refer to cellular network operators seeking to offload traffic from their cellular networks to Wi-Fi™, e.g., in peak-traffic-hours and in situations when the cellular network for one reason or another needs to be off-loaded (e.g., to provide requested quality of service, maximize bandwidth or simply for coverage).
For a wireless operator, offering a mix of two technologies that are standardized in isolation from each other presents a challenge of providing intelligent mechanisms that interact with both technologies, such as connection management.
Most current Wi-Fi™ deployments are totally separate from mobile networks, and are to be seen as non-integrated. From the UE perspective, mobile operating systems may support a simple connection management mechanism, where the UEs immediately switch all their PS (Packet Switched) bearers to a Wi-Fi™ network upon a detection of such a network with a certain signal level. The decision to offload to a Wi-Fi™ or not is referred henceforth as “access selection strategy” and the aforementioned strategy of selecting Wi-Fi™ whenever such a network is detected is known as “Wi-Fi-if-coverage”. While this may be a good strategy (e.g., for Wi-Fi™ deployed as extensions of a residential broadband connection to a fixed line operator), more is desired for mobile network operators that aim to integrate Wi-Fi as a component in their wireless networks.
In 3GPP, there have long been activities on an Access Network Discovery and Selection Function, hereinafter referred to as ANDSF. What ANDSF does is to provide policies to the UE from an ANDSF server (typically set by the operator of the currently visited or home network). These policies indicate priorities that the UE should follow when selecting an access network. For example a policy could include information to indicate that, in a certain area at a certain point in time, WLAN/Wi-Fi is preferred over a 3GPP access network. With an ANDSF server, the operator can thus distribute policies to UEs to steer access selection.
ANDSF is further described in, e.g., 3GPP TS 23.402, Architecture enhancements for non-3GPP accesses and TS 24.312, Access Network Discovery and Selection Function (ANDSF) Management Object (MO), the entire content of which is incorporated by reference herein.
As previously stated, selecting a Wi-Fi™ access point has always been executed in the UE. ANDSF does not change this, but adds a possibility to indicate a policy or preference of access selection or RAN selection based on e.g., a geographical, chronological, service or subscriber perspective. It is up to the UE to interpret and act on the policies and select an access network in either e.g., 3GPP, WLAN, WiMAX™, code division multiple access (CDMA). In 3GPP TS 24.312, all the different elements that are possible to indicate are listed. It should be noted that if a user is manually adding preferences (e.g., adding a home access point that extend a fixed broadband connection or similar as a preferred access point) then this manual configuration is expected to override any other access network selection procedure, be it ANDSF rules, algorithms in the UE's operating system, connection manager, or network controlled selection schemes.
One challenge with the ANDSF solution is that it is not set up to have any connection to any Radio Access Network (RAN) conditions. Thus, ANDSF has no support in the standard for conveniently following, for example, dynamic changes of radio conditions in the RAN. It would be good if decisions about traffic steering of a UE to either 3GPP or Wi-Fi™ could be based on more instantaneous and dynamic information about radio conditions, such that users are not unnecessarily sent to a congested access point or access technology.
Another issue that has been identified with ANDSF is that since it leaves the execution of the policies to the UE, it is not predictable (from a radio network perspective) how a UE will move between access networks, making it more difficult to optimize radio network performance.
To overcome these and other shortcomings with the ANDSF solution, a radio access network (RAN) controlled traffic steering is currently being discussed in 3GPP in relation to a study item called 3GPP/WLAN Interworking, described in 3GPP TR 37.834 Study on 3GPP/WLAN Radio Interworking and in study item description RP-122038 in 3GPP. Therein is stated that one of the objectives with a new solution is that it should be able to take dynamically changing conditions (e.g., radio access network load and performance) into account. One of the solution proposals discussed is a RAN controlled approach. With a RAN-controlled access selection, it is the network (and not the UE) that makes the decision on what access link to use for communication to or from a UE. The RAN control of traffic steering should be able to capture the dynamics in varying radio conditions as well as provide predictability to better be able to optimize radio access network performance as well as user performance.
One aspect of introducing a RAN-controlled solution for traffic steering is that of co-existence of a RAN-based, network-controlled traffic steering solution and an ANDSF-based solution. Thus, there is a question of how to harmonize a solution that fundamentally is based on the UE executing decisions and a solution that is network-controlled and network-enforced.
This question is also mentioned in the study item description referred to above and solutions that have been discussed have been to steer on different parameters and variables. For example, ANDSF could provide information that is static or semi-static in nature, and functionality in the RAN could provide more dynamic information to the UE. The problem with this approach is that the network would not ultimately be in control of the decisions as long as the final evaluation and execution is made in the UE.
Another approach has been to say that whatever solution the radio access network suggests in terms of controlling a UE's access in getting service shall override ANDSF policies if they are incompatible. This however is not optimal either, as there is information on different levels in the network and it is challenging for a RAN control to keep updated on, e.g., core network or service network information that may be relevant for traffic steering. This level of information could typically be reflected in ANDSF policies whereas it would go against what a radio network should handle to have to provide or update that knowledge to the RAN.
Thus there is a need for a traffic steering solution that can combine an ANDSF function with a network-controlled RAN solution, such that dynamics from RAN can be captured as well as policies related to services or subscriptions. For network optimization purposes, it is important to maintain the network control and predictability that such solutions offer.
Various Aspects and Embodiments that aim to address these needs are described below.